Methylnitramine (MNA) is represented by the formula CH.sub.3 NHNO.sub.2.
This is a powerful explosive, stronger than tetryl but weaker than cyclonite. It has, however, been of no practical value chiefly because its preparation is too expensive, requiring first the conversion of methylamine into urethane and then into its nitro derivative. On hydrolysis the latter yields methylnitramine. Similarly, the hydrolysis of dinitrodimethyloxamide leads to the formation of methylnitramine.
Methylnitramine is very readily soluble in water, alcohol, chloform and benzene but is less soluble in ether. It is a strong acid which easily forms salts, including explosive ones. It is not decomposed by boiling water, even in the presence of alkalis, but it is liable to destructive distillation yielding dimethylnitramine (CH.sub.3).sub.2 N--NO.sub.2, m.p. 57.degree. C., methyl alcohol, nitrous oxide and many other products.
Methylnitramine decomposes explosively in contact with concentrated sulfuric acid. It is evolved when aniline reacts with tetryl; a diphenylamine derivative is produced simultaneously. Methylnitramine reacts with picryl chloride to form tetryl.
Hereinafter the compound shall be referred to as MNA.
In the prior art methods of preparation of MNA have been excessively expensive because the yields are so low. Yields in the prior art range from about 27% to 39%.
These levels of yield can be drastically improved by the method of the instant invention.
In the prior art 1,3-dimethyl-1,3-dinitrourea from dimethylurea is prepared as follows:
1,3-Dimethyl-1,3-dinitrourea,
H.sub.3 CN(NO.sub.2)CO.N(NO.sub.2).CH.sub.3, mw 178.11, N 31.46%; liq, cap sensitive but insensitive to shock and friction; was prepared by nitrating the parent compound below 30.degree. with concentrated nitric acid or with a mixture of HNO.sub.3 and Ac.sub.2 O.
Explosive compositions of DMDU consist of: ammonium nitrate (AN) 60, ammonium perchlorate 30 and DMDU 10% (more powerful in ballistic mortar test than TNT); or AN 82, DMDU 16 and nitrocellulose (NC) 2%. A colloidal plastic compound is comprised of DMDU 31, NG 15, NC 4 and AN 50% or I 33, NC 5, AN 45 and ammonium perchlorate 17%. A propellant compound is DMDU 43, NC 50 and Ethyl Centralite 7% (Ref 4) (Compare with N,N'-dimethyl-N,N'-diphenylurea, called Centralite 2, described in Vol 2 of Encycl Explosives and Related Items, p. C137-L).